Lung cancer remains the leading cause of cancer death in industrialized countries. About 75 percent of lung cancer cases are categorized as non-small cell lung cancer (e.g., adenocarcinomas), and the other 25 percent are small cell lung cancer. Lung cancers are characterized in to several stages, based on the spread of the disease. In stage I cancer, the tumor is only in the lung and surrounded by normal tissue. In stage II cancer, cancer has spread to nearby lymph nodes. In stage III, cancer has spread to the chest wall or diaphragm near the lung, or to the lymph nodes in the mediastinum (the area that separates the two lungs), or to the lymph nodes on the other side of the chest or in the neck. This stage is divided into IIIA, which can usually be operated on, and stage IIIB, which usually cannot withstand surgery. In stage IV, the cancer has spread to other parts of the body.
Most patients with non-small cell lung cancer (NSCLC) present with advanced stage disease, and despite recent advances in multi-modality therapy, the overall ten-year survival rate remains dismal at 8-10% (Fry et al., Cancer 86:1867 [1999]). However, a significant minority of patients, approximately 25-30%, with NSCLC have pathological stage I disease and are usually treated with surgery alone. While it is known that 35-50% of patients with stage I disease will relapse within five years (Williams et al., Thorac. Cardiovasc. Surg. 82:70 [1981]; Pairolero et al., Ann, Thorac. Surg. 38:331 [1984]), it is not currently possible to identify which specific patients are at high risk of relapse.
Adenocarcinoma is currently the predominant histologic subtype of NSCLC (Fry et al., supra; Kaisermann et al., Brazil Oncol. Rep. 8:189 [2001]; Roggli et al., Hum. Pathol. 16:569 [1985]). While histopathological assessment of primary lung carcinomas can roughly stratify patients, there is still an urgent need to identify those patients who are at high risk for recurrent or metastatic disease by other means. Previous studies have identified a number of preoperative variables that impact survival of patients with NSCLC (Gail et al., Cancer 54:1802 1984]; Takise et al., Cancer 61:2083 [1988]; Ichinose et al., J. Thorac. Cardiovasc. Surg. 106:90 [1993]; Harpole et al., Cancer Res. 55:1995]). Tumor size, vascular invasion, poor differentiation, high tumor proliferate index, and several genetic alterations, including K-ras (Rodenhuis et al., N. Engl. J. Med. 317:929 [1987]; Slebos et al., N. Engl. J. Med. 323:561 [1990]) and p53 (Harpole et al., supra; Horio et al., Cancer Res. 53:1 [1993]) mutation, have been reported as prognostic indicators.
Tumor stage is an important predictor of patient survival, however, much variability in outcome is not accounted for by stage alone, as is observed for stage I lung adenocarcinoma which has a 65-70% five-year survival (Williams et al., supra; Pairolero et al., supra). Current therapy for patients with stage I disease usually consists of surgical resection and no additional treatment (Williams et al., supra; Pairolero et al., supra). The identification of a high-risk group among patients with stage I disease would lead to consideration of additional therapeutic intervention for this group, as well as leading to improved survival of these patients.